pub async fn update_ubuntu_mirror(url: &str) -> Result<(), String> {
    let sources = format!("deb {url} focal main restricted
deb {url} focal-updates main restricted");
    
    fs::write("/etc/apt/sources.list", sources)
        .map_err(|e| e.to_string())?;
    
    Command::new("apt-get")
        .args(["update"])
        .status()
        .await
        .map_err(|e| e.to_string())?;
    
    Ok(())
}